Operating a logging tool in an open (i.e., uncased) borehole can present certain difficulties. For example, if the tool penetrates the mudcake lining the wall of the borehole and exposes the underlying formation, the tool can become differentially stuck against the borehole wall. When the relatively lower pressure formation is exposed to the relatively higher pressure drilling fluid in the borehole, the drilling fluid begins to flow into the formation. If the body of the tool is adjacent the exposed formation, the tool can be drawn against the exposed part of the formation and held against the formation with several thousand pounds of force. In some cases, the amount of force holding the tool against the borehole wall may be sufficiently high to prevent removal of the tool without damage to the tool.
Standoffs and/or centralizers have been used to prevent downhole tools from becoming differentially stuck against a borehole wall. Some known standoffs are implemented as flexible strap-on devices, metal rings, fins and/or irregular portions of a tool body. Some known centralizers may be fin-shaped and/or may include extendable/retractable portions to adjust the centralizer for operation in different diameter boreholes. While the foregoing known devices may be used to help prevent downhole tools from becoming differentially stuck in a borehole, these known devices also tend to increase the envelope (e.g., the outer diameter) of the tool body and, thus, increase the risk of the tool becoming stuck in a given size borehole.